Catastrophic Climatic Consequences of Nuclear Conflict

Abstract

Despite
a two-thirds reduction in global nuclear arsenals since 1986, new scientific
research makes it clear that the environmental consequences of nuclear war can
still end human history. A series of
peer-reviewed studies, performed at several U.S. universities, predict the
detonation of even a tiny fraction of the global nuclear arsenal within large
urban centers will cause catastrophic disruptions of the global climate and
massive destruction of the protective stratospheric ozone layer. A nuclear war fought with several thousand
weapons would leave the Earth uninhabitable.

The
studies conclude that a “regional” nuclear conflict between India and Pakistan,
in which 100 Hiroshima-size weapons were exploded in the cities of those
nations, could produce as many fatalities as World War II1 and would
significantly disrupt the global climate for at least a decade. Up to 5 million tons of smoke would quickly
rise above cloud level and block about 10% of the light from reaching surface
of the Northern Hemisphere; the smoke would remain in the stratosphere for ten
years and impact average surface temperatures for more than a decade. Following
such a “regional” nuclear conflict, average surface temperatures beneath the
smoke layer would become colder than they have been in the last 1000 years,
significantly shortening growing seasons and reducing average global precipitation.2

The
combined explosive power of 100 Hiroshima-size weapons represents less than 1%
of the explosive power contained within the currently deployed and operational
US-Russian nuclear arsenals. As of 2009, virtually all of the land-based strategic
nuclear forces of both the US and Russia remain on alert and ready to launch
with only a few minutes warning.3 The
new research predicts that immense firestorms, produced by a nuclear war fought
with these weapons, could loft 150 million tons of smoke into the stratosphere.
There it rapidly would block 70% of sunlight from reaching the surface of the
Northern Hemisphere and 35% of sunlight from reaching the Southern Hemisphere.4

Under
such conditions, it would only require a matter of days or weeks for daily minimum
temperatures to fall below freezing in the largest agricultural areas of the
Northern Hemisphere. Nightly killing freezes would continue to occur for a
period of between one to three years. Average surface temperatures would become
colder than those experienced 18,000 years ago at the height of the last Ice
Age, and the prolonged cold would cause average rainfall to decrease by up to
90%. Growing seasons would be completely eliminated for more than a decade and
cause most humans and large animal populations to die of starvation.5

Deadly Climate Change from
Nuclear War

Nuclear
detonations within urban and industrial areas would ignite immense mass fires
which would burn everything imaginable and create millions of tons of thick,
black smoke (soot). This soot would ultimately be lofted into the stratosphere.
There it would absorb and block sunlight from reaching the lower atmosphere
where greenhouse gases mainly reside, and thus act to reduce the natural
greenhouse effect.6

The
profound darkness and global cooling predicted to be result of this process
(along with massive amounts of radioactive fallout and pyrotoxins7,
and ozone depletion) was first described in 1983 as nuclear winter.8 Joint research by Western and Soviet scientists led to the realization that the
climatic and environmental consequences of nuclear war, in combination with the
indirect effects of the collapse of society, could produce a nuclear winter
which would cause famine for billions of people far from the war zones.9

These
predictions led to extensive international research and peer review during the
mid-1980s. A large body of work which essentially supported the initial
findings of the 1983 studies was done by such groups as the Scientific
Committee on Problems of the Environment (SCOPE),10 the World Meteorological Organization,11 and the U.S. National
Research Council of the U.S. National Academy of Sciences.12

The
idea of nuclear winter, published and supported by prominent scientists,
generated extensive public alarm and put political pressure on the U.S. and the
U.S.S.R. to terminate a runaway nuclear arms race which, by 1986, had created a
global nuclear arsenal of more than 65,000 nuclear weapons. Unfortunately, this
was anathema to the nuclear weapons establishment and thus nuclear winter
created a backlash among many powerful conservative groups, who undertook an
extensive media campaign to brand it as “bad science” and the scientists who
discovered it as “irresponsible.”

Critics
used various uncertainties in the studies and the first climate models (which
are relatively primitive by current standards) as a basis to denigrate and
reject the concept of nuclear winter. In 1986, the Council on Foreign Relations
published an article by scientists from the National Center for Atmospheric
Research (NCAR), who predicted drops in global cooling about half as large as
those first predicted by the 1983 studies and described this as a ‘nuclear
autumn.’

Subsequent
widespread criticism, in such publications as the Wall Street Journal and Time
Magazine, often used the term “nuclear autumn” to imply that no important
climatic change would result from nuclear war. In 1987, the National Review
called nuclear winter a “fraud.” In 2000, Discover Magazine published an
article which described nuclear winter as one of “The Twenty Greatest
Scientific Blunders in History.”13

Sadly
enough, for almost two decades this smear campaign limited serious discussion
and prevented further studies of nuclear winter – and such criticism will
continue.14 Yet the basic findings of the nuclear winter research,
that extreme climatic changes would result from nuclear war, were never
scientifically disproved and have been strengthened by the latest studies.

Most
importantly, the new studies show that the original research actually underestimatedby an order of magnitude the amount of time the soot from nuclear
firestorms would remain above cloud level to block sunlight. This greatly
magnifies the impact such a global smoke layer would have on weather and
climate. The new studies clearly
demonstrate that massive changes in climate created via nuclear conflict, which
are much less severe than “nuclear winter”, would certainly have catastrophic
and devastating impacts on human populations.

Regional Nuclear Conflict Fought
with Low-Yield Nuclear Weapons

To
create the new studies, U.S. researchers used the latest NASA Goddard Institute
for Space Studies climate model (Model 1E, also used for the Intergovernmental
Panel on Climate Change), which is able to model the entire troposphere,
stratosphere, and mesosphere from the Earth’s surface up to 80 kilometers. They
simulated a small nuclear war between two countries in the sub-tropics in which
each nation attacked the other’s most densely populated urban centers with 50 Hiroshima-size (15 kiloton per weapon) low-yield nuclear
bombs.15

This
scenario is possible because the smallest nuclear weapon states today (India
and Pakistan) are each believed to possess more than 50 of these low-yield
weapons, and an arsenal of this size (or larger) could be acquired by other
nations in the near future. Thirty-two countries that do not now have nuclear
weapons own sufficient fissionable nuclear materials to construct weapons, some
in a relatively short period of time.16

U.S.
warplanners aim their extensive nuclear arsenal at a mix of military targets
(nuclear forces, conventional forces, leadership and communication facilities,
and war-supporting industries)17 and it is
assumed that Russian warplanners do the same. However, it is commonly believed
that small nuclear powers with limited arsenals are most likely to aim their
weapons at the largest cities of their adversaries.

Toon
et al. calculated that a “regional” nuclear war which employed this targeting
strategy would create 1-5 million metric tons of soot from the burning cities.18 Robock et al. used the NASA climate model to demonstrate that this soot would
be lofted to near the top of the stratosphere. 19 There the smoke
would remain, far above the area where weather occurs, for a decade – about ten
times longer than previously thought possible.

Further
modeling demonstrated that smoke particles from much larger nuclear conflicts
would also remain in the upper stratosphere for at least a decade,20 and these findings provided the basis for rejecting the conclusion of the
studies which suggested that “nuclear autumn” instead of nuclear winter would
follow a full-scale war. Robock’s team also discovered that smoke in the
sub-tropical latitudes would undergo more solar heating than smoke studied in
previous nuclear winter scenarios, and this heating would insure that the smoke
particles would be lofted into the stratosphere year-round, regardless of the
month in which the war would occur.21

Figure 1: Map showing the present principal area of Canadian wheat production and the reduction that would result from small decreases in average surface temperature21

Although
there would not be enough sunlight blocked to create a “nuclear winter”, the
massive smoke emissions from the fires of a small “regional” nuclear war would
cause a global climate change unprecedented in human history. In a matter of
days, average temperatures in the Northern Hemisphere would become colder than
any experienced during the last 1000 years.23 Growing seasons in the
middle latitudes would immediately be significantly shortened, completely
eliminating some crops that had insufficient time to reach maturity.

The
studies predict climatic consequences significantly greater and more persistent
than those which resulted from greatest volcanic eruption of the past 500
years, the 1815 Tambora eruption in Indonesia. Tambora lofted enormous amounts
of volcanic smoke particles into the stratosphere, which blocked and scattered
enough sunlight to cause the 1816 “Year Without Summer,” when killing frosts disrupted agriculture every month of the summer in
New England and widespread harvest failure and famine occurred in Europe.

The
long-term global climate, as measured by the average surface temperature over
the planet, has not varied by more than 10º C from current values during the
entire climatic history of the Earth accessible to modern science.24 Ice Ages represent periods of cooling of about 5º C below the global average
which extend for periods of thousands of years. Modern agriculture is finely
tuned to the present climate and would be severely impacted by rapid average
temperature declines of even a few degrees Celsius.

Computer
simulations of the regional nuclear conflict predict a global average surface
cooling of 1.25º C which would persist for three years, with the global average
temperature still 0.5º C below normal a decade after the war. One year after
the smoke injection there would be temperature drops of several degrees Celsius
within the grain-growing interior regions of Eurasia and North America. There
would be a corresponding shortening of growing seasons by up to 30 days and a
10% reduction in average global precipitation – which would have major impacts
on global food supplies.25

In
addition, the stratospheric smoke plumes from this regional conflict would
significantly disrupt the ozone layer. Studies by Mills, et al, predict ozone
losses of 25–45% at mid latitudes, and 50–70% at northern high latitudes
persisting for 5 years, with substantial losses continuing for 5 additional
years.26 Such levels of ozone loss have
previously been forecast only for large nuclear conflicts between the U.S. and
the former U.S.S.R.27

Severe
ozone depletion would allow intense levels of ultraviolet light to reach the
Earth even with the stratospheric smoke layer in place. It is unknown what
effects such massive increases in UV would have upon terrestrial and marine
wildlife and ecosystems.

Unfortunately,
no studies using modern climate models have yet been done to assess ozone
depletion following larger nuclear conflicts fought with high-yield strategic
nuclear weapons. This is an area of critically important research which should
receive funding.

Nuclear War Fought with
High-Yield Strategic Nuclear Weapons

Using
the vastly more modern NASA climate model and new supercomputers, in 2007
Robock et al. re-examined the climate response to a range of nuclear wars which
detonated moderate and large portions of the global nuclear arsenal in a
combination of urban, industrial, and military targets.28 The
researchers utilized data from previous studies to calculate that the
“moderate” and “large” nuclear conflicts would produce 50 and 150 million tons
of smoke,29 which they found would be lofted into the stratosphere,
where it would impact surface climate for more than a decade.30

The
“moderate” war simulation employed one third of the global nuclear arsenal
(1,667 megatons) – roughly equivalent to 60% of the explosive power contained
in the strategic nuclear weapons now kept at high-alert, launch-on-warning
status by the U.S. and Russia.31 The large war simulation used one
of the current published estimates for the total explosive power of the entire
global nuclear arsenal (approximately 5,000 megatons). However, additional research
in 2008 indicated that significantly lower total numbers of weapons and megatonnage
(explosive power) could cause the same levels of damage and climate change previously
predicted in the large war scenario.32

A
large nuclear war would produce enough smoke and soot to quickly block a very
large percentage of sunlight from reaching the surface of the entire Northern
and Southern Hemispheres. In the target areas, for the first few days after the
attack, sunlight would be reduced so much that at mid-day it would appear as dark
as a moonlit night before the war.33

Within
a matter of days, winds in the upper atmosphere would distribute this smoke and
soot around the Earth. The research predicts that 150 million tons of
stratospheric soot would block 70% of sunlight from reaching the surface of the
Northern Hemisphere and 35% of sunlight from reaching the lands of the Southern
Hemisphere.34 This smoke layer would remain the stratosphere for ten
years and its cooling effects would last for many years after it had
dissipated.

This
profound darkening of the sky would cause average global surface air
temperatures to rapidly cool by 7-8º C. Even a decade after the fires had gone out, the Earth’s average surface temperatures would be
cooled by 4º C. Both the moderate and large nuclear wars would produce cooling
equal to or greater than that experienced 18,000 years ago during the coldest
period of the last Ice Age35 – and these temperature drops would
occur abruptly in a matter of days or weeks, rather than over centuries or
millennia.

The
most recent research (December, 2008) predicts that a U.S.-Russian war which
detonated 4400 strategic nuclear weapons would put up to 180 million tons of
soot into the stratosphere.36 The resulting nuclear darkness would
cause rapid cooling of more than 20º C over large areas of North America and of
more than 30º C over much of Eurasia, including all agricultural regions
(Figure 2). Daily minimum temperatures in the world’s agricultural heartlands
would plummet below freezing for one to three years.

Figure 2: Surface Air Temperature (degree C) changes following a full-scale nuclear war averaged for June, July, and August of the year following the conflict33

Under
such conditions, it would be impossible to grow food crops for more than a
decade. Long-term consequences of the large nuclear conflict are implied by
Figure 3, which depicts predicted decreases in the growing seasons during the
third year following the conflict.

Figure 3 : Changes in the growing season (the time period with freeze-free days) in the third year following a large nuclear war which caused 150 million tons of smoke to enter the stratosphere34.

Agriculture
would be affected by not only the catastrophic drops in temperature, but also
by a dramatic decrease in sunlight (insolation) and precipitation. The cooling
of the Earth’s surface would weaken the global hydrological cycle and the
Northern Hemisphere summer monsoon circulations would collapse because the
temperature differences that drive them would not develop. Consequently, a 45%
reduction in average global precipitation is also predicted to occur.
Catastrophic climatic effects lasting for many years would occur in regions far
removed from the target areas or the countries involved in the conflict.39

Nuclear War Fought with U.S. and
Russian High-Alert Strategic Nuclear Arsenals

The
failure of the U.S. and Russia to relax their Cold War nuclear confrontation
has led each nation to continue to operate under policies that assume the
opposing side could authorize a disabling nuclear attack against them. Both
nations consequently still maintain a large fraction of their strategic nuclear
arsenals on high-alert status (in 2009, more than 2000 warheads were on
high-alert),40 with virtually all their land-based intercontinental
ballistic missiles able to be launched within 30 seconds to 3 minutes,
apparently operating under the policy of launch-on-warning.41 Thus
the “moderate” war simulated in the new research, which as noted contains a
destructive power equivalent to that contained by these high-alert arsenals,
can be ordered and executed by either of these nations in less time than it
takes to read this article.

The
2007 studies predicted that a “moderate” nuclear war which lofted 50 million tons of soot into the stratosphere
would cause average global surface air temperatures to plummet 3.5-4º C,
roughly half the drop predicted for a war which created 150 million tons of
stratospheric soot.42 Consider that average global temperature
declines of 3-4º C would prevent all grain production in Canada, and a single
night below freezing is sufficient to destroy the entire Asian rice crop.43 Because of its rapid onset, this level of climate change (although the duration
would be much briefer) would cause more stress to plant and animal life than
would a severe Ice Age.44

Climatic
changes resulting from nuclear conflict would occur many thousands of times
faster – and thus would likely be far more catastrophic – than the climatic
changes predicted as a result of global warming.45 The rapidity of
the war-induced changes, appearing in a matter of days and weeks, would allow
human populations and the whole plant and animal kingdoms no time to adapt.

It
is worth noting that the same methods and climate models used to predict global
warming were used in these studies to predict global cooling resulting from
nuclear war. These climate models have proved highly successful in describing
the cooling effects of volcanic clouds during extensive U.S. evaluations and in
international intercomparisons performed as part of the Fourth Assessment of
the Intergovernmental Panel on Climate Change.46

Predicted
drops in average global temperatures caused by a range of nuclear conflicts are
contrasted with the effects of global warming during the last 1,000 years in
Figure 4.

Global Warming
versus Global Cooling from Nuclear War

Figure 4: Northern Hemisphere average surface air temperatures anomalies during the last 1000 years contrasted with forecast temperature drops from a range of nuclear conflicts. The anomalies are with respect to the 1902-1988 Northern Hemisphere average surface air temperatures. 42

There
are, of course, other important considerations which must be made when
estimating the overall environmental and ecological impacts of nuclear war.
These must include the release of enormous amounts of radioactive fallout,
pyrotoxins, and toxic industrial chemicals into the ecosystems. A decade after
the conflict, when the smoke begins to clear, there will also be massive
increases in the amount of deadly ultraviolet light which will reach the
surface of the Earth as a result of ozone depletion. All these by-products of
nuclear war must be taken into account when comparing the danger of nuclear
conflict to other potential dangers now confronting humanity and life on Earth.

Conclusions

The
scientific studies summarized in this paper make it clear that the
environmental consequences of nuclear war threaten the continued survival of
the human species. Yet neither the U.S., nor Russia, nor any other nuclear
weapons state has ever officially evaluated what effects a war fought with
their weapons would have upon the Earth’s climate and ecosystems.

Therefore,
we cannot allow our political and military leaders to continue to ignore the
grave threats which their nuclear arsenals pose to the global environment and
human existence. The nuclear weapon
states should be required to create Environmental Impact Statements on the
likely results of the detonation of their arsenals in conflict.

The
environmental consequences of nuclear war must be included as primary
considerations in the ongoing debate about the abolition of nuclear arsenals. Without this essential information, the
debate loses the sense of necessary urgency needed to bring about fundamental
change in the nuclear status quo.

The
U.S. and Russia must recognize the senselessness of continued planning for a
nuclear first-strike which, if launched, would make the whole world – including
their own country – uninhabitable. As a first step, they should end their
preparations for the pre-emptive use of their nuclear arsenals, stand-down
their high-alert strategic nuclear forces, and eliminate the standard operating
procedure of launch-on-warning.48

Nuclear
arms control agreements can no longer focus primarily on the dismantlement of delivery
systems and fail to include the verified dismantlement of nuclear warheads.
Future negotiations must consider all the potential effects of the total number
of nuclear weapons in the nuclear arsenals.49

It
is essential that all the nuclear weapon states be convinced of the need to
honor their commitments under Article VI of the Non-Proliferation Treaty, to act
“in good faith” to eliminate their nuclear arsenals. As long as they ignore
this commitment and maintain nuclear weaponry as the cornerstone of their military
forces, they confer validity to the false idea that nuclear weapons provide
security to those who possess them, and thus encourage non-nuclear weapon
states to follow in their footsteps.

The
unalterable conclusion is that a nuclear war cannot be won and must not be
fought. Nuclear weapons must be seen not only as instruments of mass murder,
but as instruments of global annihilation which put all humanity and
civilization under a common threat of destruction.

About the Author:

Steven Starr is a Senior Scientist with Physicians for Social Responsibility, and the
Director of the Clinical Laboratory Science Program at the University of
Missouri. He has been published in the Bulletin of the Atomic Scientists and
the STAR (Strategic Arms Reduction) website of the Moscow Institute of Physics
and Technology. He can be contacted by
email at [email protected] or
through his website at www.nucleardarkness.org

Water vapor, carbon dioxide, methane,
and nitric oxide are the main greenhouse gases in the atmosphere. They allow
short wavelength solar radiation to reach the Earth but absorb radiation of
longer wavelength, which causes warming of the atmosphere. This process occurs
naturally and has kept the Earth’s temperature about 33 Celsius degrees (59
Fahrenheit degrees) warmer than it would otherwise be. Current life on Earth
could not be sustained without the natural greenhouse effect.

A term to designate toxic chemicals
released during combustion, particularly from plastics and industrial
chemicals. In a nuclear war, sources of such materials would be widespread;
mass fires in urban and industrial areas would release enormous amounts of
pyrotoxins into the air, land, and water.

John W. Birks, and Sherry L.
Stevens, Possible Toxic Environments Following a Nuclear War in: Fred Solomon
and Robert Q. Marston (eds.), The Medical Implications of Nuclear War, National
Academy of Sciences, 1986, pp. 160-161.

There are approximately 23,300
nuclear weapons in the global nuclear arsenal; 95% of these weapons belong to the
U.S. and Russia. About 8,400 of these weapons are fully operational weapons
ready for immediate use. An additional 14,900 intact nuclear weapons are in a
‘reserve’ status, with some of these scheduled for dismantlement. About 5,850
of the operational weapons are high-yield strategic nuclear weapons with an
explosive power equal to or greater than 100,000 tons of high explosive; there
are at least several thousand strategic weapons also in reserve status.

Robock et al., Nuclear winter
revisited…, op.cit., state that this is the greatest
area of uncertainty in their calculations, but note that the amount of smoke
affects the amplitude but not the timescale of the climatic response, p. 12 of
14.

Ibid., p. 3 of 14.

As of 2009, a minimum of 2200 U.S.
and Russian strategic nuclear warheads remain on high-alert status. These
include a very high percentage of the warheads on U.S. and Russian land-based
intercontinental ballistic missiles and some fraction of the warheads on U.S.
and Russian nuclear submarines. The total yield of these U.S. and Russian
high-alert strategic nuclear forces is the range of 960 to 1020 MT, which is
roughly equivalent to 60% of the explosive power of the 1,667 MT model used in
the simulations.

Launch-on-warning (LOW) is the Cold
War policy of launching a retaliatory nuclear strike while the opponent’s
missiles or warheads are believed to be in flight, but before any detonation
from the perceived attack has occurred. Early Warning Systems (EWS), high-alert
nuclear-armed ballistic missiles, and nuclear command and control systems, all
working together, provide the U.S. and Russia the capability to launch a
nuclear retaliatory strike to a perceived nuclear attack before the attack
arrives and is confirmed by nuclear detonations. However, it is the policy of
Launch on Warning, converted into standard operating procedure, which could
lead to the decision to launch solely on the basis of electronic EWS data. The
combination of capability with policy has created what is commonly referred to
as launch-on-warning status.

Robock, et al., Nuclear winter revisited…, op.cit., p. 7 of 14.

Sagan and Turco, op.cit., p. 101.

Sagan and Turco, op.cit., p. 26.

This comparison is not meant to
minimize the dangers of global warming, which warrant grave concern, rather it
is intended to make the point that the potential environmental dangers posed by
nuclear war should receive at least as much attention as is that now being
afforded to the issue of global warming.